For many parts of the nation, a prolonged period of punishing cold is just getting started.

The cold snap that descended on much of the nation from the Rockies eastward on Christmas Eve is predicted to become further entrenched and even more biting in the coming days. The worst of the cold may grip the central United States from Saturday through New Year’s Day, when temperatures may fall more than 30 degrees below normal. Then it may spill eastward.

Some of the cold could be record-challenging if the most extreme forecasts are correct.

It’s already brutal

The first cold wave arrived over the weekend into Christmas Day, infiltrating the Pacific Northwest, the Northern Rockies and much of the eastern half of the nation.

On Tuesday morning, a reinforcing blast of cold sent windchill temperatures across North Dakota and northern Minnesota crashing to around minus-40, offering just a taste of even more bitter cold to come.

Wind chill temperatures this morning are 30 below to 40 below zero and colder across North Dakota. Be careful when spending time outside! pic.twitter.com/bbnDiNv8jp

Taylor Trogdon, a meteorologist at the National Weather Service, tweeted that the American model is forecasting some of the most extreme cold “ever observed” in central Missouri, with highs below zero and lows near minus-20 around New Year’s.

This frigid air may well expand east into the Mid-Atlantic and the Northeast by New Year’s Day or shortly thereafter.

The cold waves, together, could become noteworthy for their intensity and duration. The National Weather Service is calling for New York City’s average temperature over the next seven days to be around 19 degrees, which is about 10 degrees below average.

An arctic chill will be with us through at least New Year's Weekend. The forecast average temperature at Central Park is 19°F degrees. We do not expect temperatures to rise above the freezing mark for at least the next 7 days. pic.twitter.com/G2ff161EPv

Just how cold will your city be? Here is the American modeling system’s (ensemble mean) forecast for the coldest day between Wednesday and New Year’s Day:

Minneapolis: Saturday. High: minus-9, low: minus-15

Milwaukee: Saturday. High: 6, low: minus-2

St. Louis: Sunday. High: 1, low: Minus-9

Oklahoma City: Monday. High: 9, low: minus-1

Dallas: Monday. High: 20, low: 11

Chicago: Saturday. High: 4, low: minus-1

Detroit: Monday. High: 14, low: 4

Cleveland: Monday. High: 15, low: 11

Indianapolis: Monday. High: 6, low: minus-5

Memphis: Monday. High: 16, low: 9

Boston: Wednesday. High: 11, low: 6

New York: Monday. High: 17, low: 6

Pittsburgh: Monday. High: 15, low: 4

Washington: Monday. High: 20, low: 10

Raleigh, N.C.: Monday. High: 26, low: 15

Atlanta: Monday. High: 35, low: 20

Keep in mind that model forecasts, so far this year, have tended to run colder than reality beyond three days into the future. So it remains to be seen whether the cold will be this intense.

But irrespective of its exact magnitude, models are in strong agreement that the abnormally cold period will last for a while — at least the next week to 10 days. After that, there may be a gradual thaw.

Jason SamenowJason Samenow is The Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association. Follow